Safety attachment for lawn mowers

ABSTRACT

A safety attachment is provided for use with a rotary lawn mower to prevent substantial injury to anyone whose extremity may accidentally strike the cutter. The attachment includes a relatively large annular disc mounted to the drive shaft of the motor for rotation about a vertical axis and at least one cutter bar mounted diametrically across the disc on the underside thereof. The disc diameter is substantially equal to the length of the cutter bar. In one embodiment slots are provided adjacent to the leading edges of the cutter bar and impellers are provided on the upper side of the disc adjacent the slot for discharging cut grass through the side of the machine. The combination of the disc and the cutter bar provides good grass cutting action and at the same time greatly reduces the risk of serious injury in the event that one&#39;s foot, for example, accidentally slips in under the mower.

CROSS-REFERENCE TO RELATED APPLICATION

This is a .Iadd.reissue of Ser. No. 853,045, now U.S. Pat. No.4,171,608, which is a .Iaddend.continuation-in-part of abandonedapplication Ser. No. 729,113, filed Oct. 4, 1976, entitled "SafetyAttachment for Lawn Mowers".

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to rotary lawn mowers and moreparticularly is directed towards a new and improved .[.safetyattachment.]. .Iadd.relatively safe cutting structure .Iaddend.forrotary lawn mowers.

2. Description of the Prior Art

Rotary lawn mowers are becoming increasingly more popular as compared toreel type lawn mowers primarily for the reason that rotary lawn mowersare mechanically simpler, generally less expensive, lighter and easierto service than a reel type lawn mower. Despite the many advantages ofthe rotary type lawn mower, it is somewhat dangerous to use because thecutting blade rotates at a high speed and serious injuries frequentlyoccur as the result of persons accidentally or negligently getting theirfoot or hand in under the lawn mower while it is operating. The highspeed blade can easily sever a finger or toe even through work shoes.

While various devices have been developed heretofore to prevent injuriesof this type by rotary lawn mowers; none of them has been entirelysatisfactory from the standpoint of effectiveness, simplicity, ease ofmaintenance and other factors.

Accordingly, it is an object of the present invention to provide a newand improved safety attachment for rotary lawn mowers. Another object ofthis invention is to provide a simple, low-cost safety attachment forlawn mowers which is quickly and easily installed and may be provided asoriginal equipment or as an attachment for existing lawn mowers. Anotherobject of this invention is to provide a safety cutter assembly for arotary lawn mower in which a single cutting bar may provide freshcutting edges by simply changing the position of the bar.

SUMMARY OF THE INVENTION

This invention features a .[.safety attachment.]. .Iadd.relatively safecutting structure .Iaddend.for rotary type lawn mowers comprising anannular disc mountable to the lower end of the drive shaft of the mowermotor and a cutter bar having a length substantially equal to thediameter of the disc mounted flush against the disc diametrically acrossthe underside thereof. In one embodiment the disc is provided with slotsadjacent the leading edges of the cutter bar and air scoops are providedon the upper side of the disc proximate to the slots to discharge grasscuttings from the side of the machine. The cutter bar is rectangular incross section and has four cutting edges which may be brought to bear bychanging the position of the bar.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view in perspective of a safety attachment for a rotary typelawn mower made according to the invention,

FIG. 2 is a cross-sectional view taken along the lines 2--2 of FIG. 1,

FIG. 3 is a sectional view in side elevation showing the attachmentmounted to a standard rotary lawn mower,

FIG. 4 is a view in perspective, partially broken away, of a lawn mowerequipped with the attachment,

FIG. 5 is a view in perspective showing a modification of theattachment,

FIG. 6 is a cross-sectional view taken along the lines 6--6 of FIG. 5,

FIG. 7 is a bottom plan view showing a further modification of theinvention,

FIG. 8 is an exploded perspective view showing yet another modificationof the invention,

FIG. 9 is a view in side elevation thereof,

FIG. 10 is an exploded perspective view showing still anothermodification of the invention,

FIG. 11 is a bottom plan view thereof, and,

FIG. 12 is a view in side elevation thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, the reference character 10 generallyindicates a rotary lawn mower comprised of a housing 12 mounted onwheels 14 and directed by a handle 16. A motor 18, either gasoline orelectric, is mounted on top of the housing, and its drive shaft 20extends down through the top of the housing to rotate a safety cutterattachment 22 at a high speed about a vertical axis. The housing 12 isentirely open across its bottom and the grass is cut by the rotatingcutter attachment 22 to a height determined by the position of thewheels 14.

The safety cutter attachment 22, according to the invention, iscomprised of an annular disc 24 mounted coaxially to the lower end ofthe drive shaft 20 and a cutter bar 26 mounted diametrically across thelower face of the disc 24. The diameter of the disc 24 should not beless than the length of the cutter bar and preferably the disc diameterand cutter bar length are substantially equal so that the peripheraledge of the disc 24 is substantially even with the ends of the cutterbar 26.

The disc 24 is relatively stiff and may be fabricated from a variety ofmaterials, such as aluminum, fiberglass, suitable high impact plastics,or other materials which are relatively stiff, tough and will notshatter. The diameter of the disc is made to match the length of thecutter bar which the mower housing is designed to accommodate. By way ofexample, for a standard size 18" rotary lawn mower, a disc 18" indiameter is employed. The disc may have a thickness of perhaps 1/4" iffabricated from aluminum, magnesium or the like, or may be thinner iffabricated from steel. The cutter bar 26 has a length of 18" and isfastened diametrically across the lower face of the disc as by 3/4"bolts 28 threaded into nuts 30 and spaced diametrically across the disc.Typically, four such nuts and bolts are sufficient to hold the cutterbar 26 flat against the face of the disc. The disc, together with thecutter bar, commonly are mounted to the drive shaft 20 by means of a nut32 engaging the threaded lower end of the drive shaft.

Preferably, the cutter bar is made of steel to provide a long lastingcutting edge. Typically the cutter bar may be perhaps 2" wide by 1/4"thick, although these dimensions obviously may be varied. While theforward and leading edges of the cutter bar may be tapered to provide anacute angle cutting edge, it has been found that the cutter bar workseffectively if the cutter bar is a true rectangle in cross-section sothat the leading and trailing edges are perpendicular to the upper andlower faces of the cutter bar. Using a cutter bar of rectangularcross-section, it is possible to use the bar for a much longer periodbetween sharpenings than would otherwise be the case. Since only theleading lower corners of the cutter bar become worn when the lawn moweris in use, it is possible to detach the cutter bar from the disc and byturning the bar appropriately and remounting it, a fresh, sharp cuttingedge may be brought to bear. All four corners of the cutter bar may thusbe put to use before it becomes necessary to remove the cutter bar andsharpen it. In practice, the outer ends of the cutter bar should beslightly rounded, particularly at the corners, to reduce the risk ofserious injury by that portion of the attachment in the event that aperson comes in contact with the device.

While it has been found that a flat, imperforate disc and cutter barassembly will cut grass, the cutting action is greatly improved byforming slots 34 through the disc directly above and in advance of theleading edge of the cutter bar. The slots typically may be 1/2" wide and7" in length and serve to provide an air flow up through the disc. Thisair flow helps to raise the blades of grass so that they will be trimmedto the same height by the cutter bar as it rotates with the disc.

The air flow is further enhanced and the discharge of the grass outthrough the side of the mower is aided by means of fan blades 36 on topof the disc extending lengthwise of the slots 34 behind the trailingedges thereof. The blades preferably are in the form of concave,semi-cylindrical segments which may be formed integral with the disc asby stamping the segments out of the disc to form the slots.Alternatively, the blades may be formed by tubing sectors 38, assuggested in FIGS. 5 and 6, and mounted diametrically along the top ofthe disc by means of the same nuts and bolts that mount the cutter bar.The width of the blades might be on the order of perhaps 1/2" or so andprovide sufficient fanning action to discharge the cut grass out theside chute of the mower.

In order to reduce the weight of the disc and aid in the air flow, thedisc may be formed with a number of perforations 40 which might bearranged in radial array as shown in FIG. 1.

Referring now to FIG. 7 of the drawings, there is illustrated a furthermodification of the invention and in this embodiment cutter bars 42 and44 are arranged in a cross at right angles to one another. The cutterbars thus provide four active cutting edges to improve the cuttingaction of the attachment. Each of the cutter bars is adapted to beinverted and reversed so that a fresh cutting edge may be brought tobear four times for each cutter bar before it becomes necessary tosharpen the cutters. As before, the cutters are mounted to the bottomface of the disc 46, the diameter of which corresponds with the lengthsof the cutters. As before, the disc is formed with slots 48 directlyabove the leading edges of the cutter bars. Fan blades similar to thosedescribed in conjunction with the principal embodiment may also beemployed on the upper face of the disc.

Referring now to FIGS. 8 and 9 of the drawings, there is illustratedanother modification of the invention and in this embodiment a straight,standard cutter bar 50 is secured to the underside of a disc 52 by meansof a standard bolt 54. The disc 52 has a diameter substantiallycorresponding to the length of the cutter bar and is formed with adiametrical groove 56 of a width corresponding to the width of thecutter bar and of a depth somewhat less than the thickness of the cutterbar so that the bar, when mounted in the groove and fastened to thedrive shaft of the motor, will appear as is shown in FIG. 9 with itsleading cutting edge 58 extending below the bottom surface of the disc.By forming a groove in the disc and locating the cutter bar within thegroove, there will be no relative movement between the cutter bar andthe disc when the machine is operated.

In this embodiment the disc may be solid throughout, with the exceptionof a central opening 60 through which the bolt passes. The assemblyprovides a good cutting action and a simple means for locking the bladeto the disc. It has been found that it is not necessary for the grass toextend up above the cutting edge in order to produce a cutting actionand, in practice, the device of FIGS. 8 and 9 works well in mowing wetgrass and high weeds and tends to keep itself in a very clean condition.Because of the solid nature of the disc, the mower continues atsubstantially the same speed and does not hesitate even in the thickestof grass or high weeds. In a conventional rotary mower, on the otherhand, deep grass must be cut very slowly to prevent stalling themachine, and using the solid disc, the grass tends to lay down somewhatand then is cut. Since the grass does not extend up across the full faceof the cutter bar, it has also been found that the cutting edge tends toremain much sharper for longer periods of time than a conventionalblade.

Referring now to FIGS. 10, 11 and 12, there is illustrated yet anothermodification of the invention, and in this embodiment a straight cutterbar 62 is connected to a solid disc 64 by means of a bolt 66 passingthrough the center of the cutter bar and the disc. The cutter bar anddisc are locked against relative movement by means of a pair of spacedstuds 68 and 70 extending from the bottom face of the disc and engagingthe cutter bar 62 through keyhole openings 72 and 74 formed nearopposite ends of the cutter bar. The cutter bar is connected to the discby placing the bar so that the heads of the studs pass through thelarger ends of the keyhole openings, in which position the bar will beslightly offset. The bar is then placed flush against the surface of thedisc and slipped sidewise so that the smaller portions of the keyholeopenings pass in under the heads of the studs with the center opening 76of the cutter bar and the center opening 78 of the disc now inalignment. The bolt 66 is then installed and connected to the driveshaft of the mower. The assembly has operating characteristics similarto the device of FIGS. 8 and 9, and the disc is easily separated fromthe cutter bar to periodically service the bar or replace it asrequired.

In the event that a person, such as the operator pushing the lawn mower,accidentally places his foot under the housing he will not be seriouslyinjured by the attachment by virtue of the disc preventing the foot fromcoming into the full path of the cutters. It has been found that, insuch cases where the foot does accidentally move in under the mower,some scuffing of the shoe occurs but no serious injury is done to thefoot.

While the invention has been described with particular reference to theillustrated embodiments, numerous modifications thereto will appear tothose skilled in the art.

Having thus described the invention, what I claim and desire to obtainby Letters Patent of the United States is:
 1. A safety attachment for arotary lawn mower having a motor and a drive shaft mounted thereto,comprising:a generally rigid disc mountable to the lower end of saidshaft, the underside of said disc presenting a substantially flat,smooth continuous surface and the periphery thereof presenting a smooth,continuous substantially circular edge; and a cutter bar havingsubstantially planar upper and lower surfaces and being detachablymounted diametrically across and with said upper surface directlyflushly against the underside surface of said disc over substantiallythe full upper surface of the bar, the length of said cutter bar beingsubstantially equal to the diameter of said disc with the ends of said.[.bars.]. .Iadd.bar .Iaddend.being substantially even with theperipheral edge of said disc, said cutter bar being rectangular in crosssection, each longitudinal edge of said bar providing a cutting edgewhen in cutting position with respect to said disc, the cutting positionof each longitudinal edge being that position occupied by saidlongitudinal edge when disposed at a lower forward edge of said barrelative to the direction of rotation of said disc and said bar, the baracting in a horizontal cutting plane to cut material brought intocontact therewith.
 2. A safety attachment, according to claim 1,including at least a second cutter bar diametrically and detachablymounted to and directly flat against the lower face of said disc andintersecting said first bar.
 3. A safety attachment, according to claim1, wherein the bar is straight.
 4. A safety attachment, according toclaim 1, and further comprising releasable connecting means fordetachably mounting said bar to said disc.
 5. A safety attachment for arotory lawn mower having a motor and drive shaft mounted thereto,comprising:a disc mountable to the lower end of said shaft, theunderside of said disc presenting a substantially planar, continuoussurface with the periphery of the disc presenting a continuoussubstantially circular edge; a cutter bar mounted diametrically acrossthe underside of said disc, full upper surfaces of the cutter bar beingmounted flushly against the underside surface of said disc, a lowerforward edge of said bar acting in a horizontal cutting plane to cutmaterial brought into contact therewith, the length of said cutter barbeing substantially equal to the diameter of said disc with the ends ofsaid bar being substantially even with the peripheral edge of said disc;and releasable connecting means for detachably mounting said bar to saiddisc.
 6. A safety attachment, according to claim 5, wherein saidconnecting means includes a groove formed diametrically across theunderside of said disc, said groove having a depth less than thethickness of said bar.
 7. A safety attachment, according to claim 5,wherein said connecting means includes a pair of diametrically spacedstuds mounted to the underside of said disc, said bar being formed witha pair of longitudinally spaced openings adapted to receive said studswhen said bar is in position against said disc.
 8. A safety attachment,according to claim 7, wherein said openings are keyhole shaped. .Iadd.9. A cutting structure for a rotary lawn mower having a motor and adrive shaft mounted thereto, comprising:a generally rigid disc mountableto the lower end of said shaft, the underside of said disc presenting asubstantially flat, smooth continuous surface and the periphery thereofpresenting a smooth, continuous substantially circular edge; and acutter bar having substantially planar exterior surfaces and beingmounted diametrically across and directly flushly against the undersidesurface of said disc over substantially the full upper surface of thebar, the length of said cutter bar being substantially equal to thediameter of said disc with the ends of said bar being substantially evenwith the peripheral edge of said disc, said cutter bar being rectangularin cross section, at least certain longitudinal edges of said barproviding cutting edges, the bar acting in a cutting plane to cutmaterial brought into contact therewith. .Iaddend..Iadd.
 10. A cuttingstructure for a rotary lawn mower having a motor and a drive shaftmounted thereto, comprising: a generally rigid disc mountable to thelower end of said shaft, the underside of said disc presenting asubstantially flat surface and the periphery thereof presenting asubstantially circular edge; and, a cutter bar carried by the disc andextending diametrically across the disc against the underside surface ofsaid disc, the length of said cutter bar being substantially equal tothe diameter of said disc with the ends of said bar being substantiallyeven with the peripheral edge of said disc, said cutter bar beingrectangular in cross section, at least certain longitudinal edges ofsaid bar providing cutting edges, the bar acting in a cutting plane tocut material brought into contact therewith. .Iaddend. .Iadd.
 11. Acutting structure for a rotary lawn mower having a motor and a driveshaft mounted thereto, comprising: a generally rigid disc mountable tothe lower end of said shaft, the underside of said disc presenting asubstantially flat surface and the periphery thereof presenting asubstantially circular edge; and a cutter bar having substantiallyplanar upper and lower surfaces and being mounted diametrically acrossand with said upper surface directly flushly against the undersidesurface of said disc over at least medial portions of the full uppersurface of the bar, the length of said cutter bar being substantiallyequal to the diameter of said disc with the ends of said bars beingsubstantially even with the peripheral edge of said disc, said cutterbar being rectangular in cross section, at least certain longitudinaledges of said bar providing cutting edges, the bar acting in a cuttingplane to cut material brought into contact therewith. .Iaddend..Iadd.12. In a rotary mower having a motor and a drive shaft mounted thereto,a cutting structure mounted for rotary movement with the drive shaft,comprising: a substantially rigid disc portion carried by the driveshaft; and, a cutter bar portion carried by the disc portion on a facethereof facing material which is to be mowed, the cutter bar portionextending in a material cutting mode across the disc portion without theends of said cutter bar portion extending beyond the peripheral edge ofthe disc portion. .Iaddend. .Iadd.
 13. In the rotary mower of claim 12wherein the cutter bar portion is uniform in thickness and lowersurfaces of the cutter bar portion are spaced from the underside of thedisc portion a distance equal to the thickness of the cutter barportion. .Iaddend..Iadd.
 14. In the rotary mower of claim 12 whereinlower surfaces of the cutter bar portion are spaced from the undersideof the disc portion a distance equal to the greatest thickness of thecutter bar portion. .Iaddend..Iadd.
 15. In the rotary mower of claim 12wherein the cutter bar portion is rectangular in cross section, at leastcertain edges of said bar providing cutting edges, the bar acting in acutting plane to cut material brought into contact therewith..Iaddend..Iadd.
 16. In the rotary mower of claim 12 wherein at leastmedial portions of the cutter bar portion are contiguous with said faceof the disc portion. .Iaddend..Iadd.
 17. In the rotary mower of claim 12wherein the cutter bar portion is contiguous along its length with saidface of the disc portion. .Iaddend. .Iadd.
 18. In the rotary mower ofclaim 12 and further comprising means carried by the disc portion forcreating an air flow sufficient to discharge mowed material from themower. .Iaddend..Iadd.
 19. In the rotary mower of claim 12 and furthercomprising means operable with the disc portion and drive shaft forcreating an air flow sufficient to discharge mowed material from themower. .Iaddend..Iadd.
 20. In the rotary mower of claim 12 wherein thecutter bar portion is rectangular in cross section at least at medialportions thereof. .Iaddend..Iadd.
 21. In the rotary mower of claim 12wherein the disc portion and cutter bar portion are disposed and rotatein a substantially horizontal plane to face material which is to bemowed. .Iaddend..Iadd.
 22. In the rotary mower of claim 12 wherein thecutter bar portion extends diametrically across the disc portion and issubstantially equal in length to the diameter of the disc portion..Iaddend..Iadd.
 23. In the rotary mower of claim 12 wherein the cutterbar portion extends across the disc portion at its longest dimension andis substantially equal in length to said longest dimension. .Iaddend..Iadd.
 24. In the rotary mower of claim 12 wherein the surface of thedisc portion facing the material which is to be mowed is provided with agroove within which at least a portion of the cutter bar portion isreceived to facilitate mounting of the cutter bar portion to the discportion. .Iaddend..Iadd.
 25. In the rotary mower of claim 12 whereinsurface portions of the cutter bar portion are planar. .Iaddend. .Iadd.26. In the rotary mower of claim 12 wherein the cutter bar portionextends diametrically across the disc portion. .Iaddend..Iadd.
 27. Inthe rotary mower of claim 26 wherein at least medial portions of thecutter bar portion are contiguous with said face of the disc portion..Iaddend..Iadd.
 28. In the rotary mower of claim 26 wherein the cutterbar portion is contiguous along its length with said face of the discportion. .Iaddend..Iadd.
 29. In the rotary mower of claim 12 and furthercomprising means for mounting the cutter bar portion to the disc portionto prevent extension of the ends of the cutter bar portion beyond theperipheral edge of the disc portion. .Iaddend..Iadd.
 30. A cuttingstructure adapted to be mounted for rotary movement with a drive shaft,comprising: a substantially rigid disc portion carried by the driveshaft; and a cutter bar portion carried by the disc portion on one facethereof, the cutter bar portion extending in a material cutting modeacross the disc portion without the ends of said cutter bar portionextending beyond the peripheral edge of the disc portion. .Iaddend..Iadd.
 31. The cutting structure of claim 30 wherein the cutter barportion extends diametrically across the disc portion. .Iaddend..Iadd.32. The cutting structure of claim 30 and further comprising means formounting the cutter bar portion to the disc portion to prevent extensionof the ends of the cutter bar portion when the cutter bar portion is ina material cutting mode beyond the peripheral edge of the disc portion..Iaddend..Iadd.
 33. The cutting structure of claim 30 wherein thecutting structure is adapted to be mounted for rotary movement with thedrive shaft of a rotary mower, the disc portion and the cutter barportion being disposed and rotating in a substantially horizontal planeto face material which is to be mowed. .Iaddend..Iadd.
 34. In a rotarymower having a motor and a drive shaft mounted thereto, a cuttingstructure mounted for rotary movement with the drive shaft, comprising:a substantially rigid disc portion carried by the drive shaft; and acutter bar portion carried by the disc portion on a face thereof facingmaterial which is to be mowed, the cutter bar portion extendingdiametrically across the disc portion without the ends of said cutterbar portion extending beyond the peripheral edge of the disc portion..Iaddend..Iadd.
 35. In the rotary mower of claim 34 wherein the cutterbar portion is substantially equal in length to the diameter of the discportion. .Iaddend. .Iadd.
 36. A cutting structure adapted to be mountedfor rotary movement with a drive shaft, comprising: a plate portioncarried by the drive shaft; and, a cutter bar portion carried by theplate portion on one face thereof, at least portions of the cutter barportion being flush with said face, the cutter bar portion extendingacross the plate portion at its longest dimension and beingsubstantially equal in length to the longest dimension of the plateportion. .Iaddend..Iadd.
 37. The cutting structure of claim 36 whereinthe plate portion is substantially circular and wherein the cutter barportion extends diametrically across the plate portion. .Iaddend..Iadd.38. The cutting structure of claim 36 wherein the plate portion issubstantially circular in conformation. .Iaddend. .Iadd.
 39. In a rotarymower having a motor and a drive shaft mounted thereto, a cuttingstructure mounted for rotary movement with the drive shaft, comprising:a substantially rigid disc portion carried by the drive shaft; and acutter bar portion carried by the disc portion on a face thereof facingmaterial which is to be mowed, the cutter bar portion extending acrossthe disc portion at the longest dimension of the disc portion and beingsubstantially equal in length to said longest dimension, the ends ofsaid cutter bar portion lying within the extent of the peripheral edgeof the disc portion. .Iaddend..Iadd.
 40. A cutting structure adapted tobe mounted for rotary movement with a drive shaft, comprising: asubstantially circular plate portion carried by the drive shaft; and, acutter bar portion carried by the drive shaft, at least medial portionsof the cutter bar portion being disposed flushly against one face of theplate portion, the cutter bar portion extending diametrically across theplate portion without the ends of said cutter bar portion extendingbeyond the peripheral edge of the plate portion. .Iaddend. .Iadd. 41.The cutting structure of claim 40 wherein the cutter bar portion iscontiguous along its length with said face of the plate portion..Iaddend..Iadd.
 42. The cutting structure of claim 40 wherein said faceof the plate portion faces material which is to be mowed and the plateportion and cutter bar portion rotate on the drive shaft in asubstantially horizontal plane. .Iaddend..Iadd.
 43. The cuttingstructure of claim 40 wherein the cutter bar portion is contiguous alongits length with said face of the plate portion. .Iaddend..Iadd.
 44. Thecutting structure of claim 43 wherein said face of the plate portionfaces material which is to be mowed and the plate portion and cutter barportion rotate on the drive shaft in a substantially horizontal plane..Iaddend..Iadd.
 45. The cutting structure of claim 44 wherein the plateportion is substantially circular in conformation. .Iaddend.